This is a much better idea than a GROWTH modifier. You should contact the mod author. He's around. The only consideration is that, if you do it this way, it makes sense to have a mechanic to deliberately limit base growth of individual bases past a certain point. This is SMAC, so there should be tradeoffs.
Which mod, tho? You said you didn't remember which mod did it.
I was thinking more than one effect on social engineering. Say, GROWTH and EFFIC penalties. Maybe POLICE too, but my idea was that more POLICE would help in that regard. Essentially, without a Hab Complex or the like, your colony becomes a dystopic Hive City, like somesort of Space Kowloon.
All that being said, I still think SMAC's assumption that populations just... grow... to be pretty outdated in a world where every competent population is collapsing from lack of fertility. Democracy makes you have more children? Planned economics? Totalitarian chinkism? Lol, c'mon man!
True. Through you do have to remember that the world of SMAC is different from ours.
Even then, SMAC populations are fairly small, AFAIK every population point = 10k people. It's actually kinda weird when a large population late in the game has a few millions population and is somehow polluting enough to doom the world, even through something like ten million is chump change compared to the kind of populations a world can systain.
I think SMAC is also built on a lot of 80s-90s tropes, which is why you have the assumption populations just grown.
I agree that Democracy giving more growth is a bit weird. Planned doing that makes more sense.
Hive having large grown makes sense in light of Mao's pro-fertility campaigns and the fact life in the Hive seems pretty sparse and ascetic. Hive is the "Quantity > Quality" and "Harmony Above All" Eastern Chinkoid Horde faction, after all. They would be absolutely vile if Sheng-ji Yang didn't actually make some pretty cool points in his quote.
Believers are the faction that should have the GROWTH bonus and Fundamentalism is the appropriate Politics tier. The other one shouldn't be in economics. It would fit best in Power because if your faction values being strong more than increasing knowledge or accumulating possessions that's more likely to lead to patriarchal (large) family formation.
You know, Believers having a Growth bonus would actually make more sense.
The thing with Fundie is that its the big WAR Politics choice. Then again, does anyone aside Believers and an earlier rusher Sparta run fundie? It gimps your research pretty bad.
POWER having more growth is an interesting idea, but again you hit the problem of POWER being a pure war-focused choice.
Another big issue is that almost all options do "2 bonuses, 1 penalty", with the exception being Free Market because it's so damn good.